This invention relates generally to printer-slotters for printing and slotting carton blanks which are usually of double-face corrugated paperboard. More particularly, the present invention is directed to a phase register control to maintain registration of operating shaft mounted cylinders during the fitting of a printing die or adjustment of the slotter heads.
In a conventional printer-slotter machine, each operation is performed successively by a module or section which may be opened for the fitting of attachments, cleaning and servicing. When the modules are in the closed position for operation, power is transmitted from a main drive motor in the feed end module by means of intermeshing gears in each module. If the printing module, for example, is separated from its adjustment modules, the power train gears are exposed and free to rotate.
When servicing the modules, the usual practice is for the operator to separate the modules so that the cylinders are readily accessible. In changing a printing die, for instance, the die is fastened to the print cylinder by staples or special clamps. Because of the length of the die, it is customary to rotate the cylinder to mount the die on the cylinder so that both ends of the die may be secured. Rotation of the cylinder affects the register of that station with respect to the rest of the machine. Similar problems may occur with the slotter cylinders or, if present, the die cutting cylinders, during set-up or adjustment of those machine sections, such that the cylinders will not mesh in register when the modules are reclosed.
To overcome this problem, timing marks have been placed on the cylinder shaft gears. Before the sections are reclosed, the gears are rotated (by hand, crank or otherwise) so that the timing marks are brought or set into proper relative alignment. This alignment must be maintained while the gears are re-engaged and the modules reclosed. If the operator forgets to set the timing prior to closing the machine, the initial sheets will be scrap and the machine will have to be opened again and the timing set correctly by rotating the gears. This is a time-consuming operation because trials must be made and blanks examined to establish that the proper relationship exists between a given cylinder and the cylinders in the remaining sections. The change may or may not be noted by the operator upon visual inspection of the gear timing marks. To restore the proper phase relationship, the sections must be decoupled again and the gear associated with the displaced cylinder shaft must be rotated to bring the timing mark back into alignment. If the change is not noted by the operator upon visual inspection of the gears, the machine will produce scrap sheets wherein the slots and/or printing are not correctly registered on each blank. An operator, upon noticing this condition must shut down the machine and then rotate the cylinders and gears so as to bring the elements into alignment. The result is a significant loss in production time and material.
Various mechanisms for setting the phase adjustment are well known in the industry. One type of mechanism is shown in U.S. Pat. No. 2,677,971. Other mechanisms may comprise a harmonic differential, a worm gear differential or the like. A worm gear differential is described in U.S. Pat. No. 3,003,403.
Numerous solutions have been proposed to insure alignment of the operating elements during separations of the modules. U.S. Pat. No. 2,975,706 for Printer Slotter Machine describes an arrangement in which each module is coupled to a splined shaft extending the length of the opened machine.
U.S. Pat. No. 2,866,408 for a Transmission Device for Rotary Printing Machines employs an analogous shaft provided with a beveled gear which may be coupled to each module.
Another arrangement is for a gear locking mechanism as in U.S. Pat. No. 3,611,925 Printer Slotter Module Gear Train Brake.
To eliminate the manual operations described above, a solution has been proposed in U.S. Pat. No. 4,527,788 issued July 9, 1985. In that patent, the machine sections are independently driven so as to eliminate the gear coupling between sections. The phase relationship between the shaft cylinders is then controlled electronically both at set up and during dynamic operation of the machine under normal conditions. The solution proposed in the patent requires a relatively sophisticated but unreliable and expensive electronic control and individual variable speed drives.